Antibacterial activity of Onions (Allium cepa) against Staphylococcus aureus and Escherichia coli

Abstract

Onion (Allium cepa) is among the oldest cultivated plants, and is used for many things. Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli) was tested against Allium cepa extracts to determine the antibacterial activity. The antimicrobial effects of the aqueous extract against these bacteria species was carried out in vitro by using the agar well diffusion method. The extract was found to be effective at the concentration of 2000mg/ml against Staphylococcus aureus and Escherichia coli with the zone of inhibition of 4.5mm each respectively and was least effective at the concentration of 400mg/ml against Staphylococcus aureus and Escherichia coli with zone of inhibition of 3.5 and 2.5mm respectively. Minimum inhibitory concentration of 1000mg/ml was obtained for the aqueous extract on both bacteria. The results showed that the aqueous extract of onions had very minimal inhibitory effect on both tested bacteria.